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'\" Copyright (c) 1993 The Regents of the University of California.

'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.

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'\" RCS: @(#) $Id: switch.n,v 1.1.1.1 2002-01-16 10:25:25 markom Exp $

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.so man.macros

.TH switch n 7.0 Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

switch \- Evaluate one of several scripts, depending on a given value

.SH SYNOPSIS

\fBswitch \fR?\fIoptions\fR?\fI string pattern body \fR?\fIpattern body \fR...?

.sp

\fBswitch \fR?\fIoptions\fR?\fI string \fR{\fIpattern body \fR?\fIpattern body \fR...?}

.BE

.SH DESCRIPTION

.PP

The \fBswitch\fR command matches its \fIstring\fR argument against each of

the \fIpattern\fR arguments in order.

As soon as it finds a \fIpattern\fR that matches \fIstring\fR it

evaluates the following \fIbody\fR argument by passing it recursively

to the Tcl interpreter and returns the result of that evaluation.

If the last \fIpattern\fR argument is \fBdefault\fR then it matches

anything.

If no \fIpattern\fR argument

matches \fIstring\fR and no default is given, then the \fBswitch\fR

command returns an empty string.

.PP

If the initial arguments to \fBswitch\fR start with \fB\-\fR then

they are treated as options.  The following options are

currently supported:

.TP 10

\fB\-exact\fR

Use exact matching when comparing \fIstring\fR to a pattern.  This

is the default.

.TP 10

\fB\-glob\fR

When matching \fIstring\fR to the patterns, use glob-style matching

(i.e. the same as implemented by the \fBstring match\fR command).

.TP 10

\fB\-regexp\fR

When matching \fIstring\fR to the patterns, use regular

expression matching

(i.e. the same as implemented by the \fBregexp\fR command).

.TP 10

\fB\-\|\-\fR

Marks the end of options.  The argument following this one will

be treated as \fIstring\fR even if it starts with a \fB\-\fR.

.PP

Two syntaxes are provided for the \fIpattern\fR and \fIbody\fR arguments.

The first uses a separate argument for each of the patterns and commands;

this form is convenient if substitutions are desired on some of the

patterns or commands.

The second form places all of the patterns and commands together into

a single argument; the argument must have proper list structure, with

the elements of the list being the patterns and commands.

The second form makes it easy to construct multi-line switch commands,

since the braces around the whole list make it unnecessary to include a

backslash at the end of each line.

Since the \fIpattern\fR arguments are in braces in the second form,

no command or variable substitutions are performed on them;  this makes

the behavior of the second form different than the first form in some

cases.

.PP

If a \fIbody\fR is specified as ``\fB\-\fR'' it means that the \fIbody\fR

for the next pattern should also be used as the body for this

pattern (if the next pattern also has a body of ``\fB\-\fR''

then the body after that is used, and so on).

This feature makes it possible to share a single \fIbody\fR among

several patterns.

.PP

Below are some examples of \fBswitch\fR commands:

.CS

\fBswitch\0abc\0a\0\-\0b\0{format 1}\0abc\0{format 2}\0default\0{format 3}\fR

.CE

will return \fB2\fR,

.CS

\fBswitch\0\-regexp\0aaab {

        ^a.*b$\0\-

        b\0{format 1}

        a*\0{format 2}

        default\0{format 3}

}\fR

.CE

will return \fB1\fR, and

.CS

\fBswitch\0xyz {

        a

                \-

        b

                {format 1}

        a*

                {format 2}

        default

                {format 3}

}\fR

.CE

will return \fB3\fR.

.SH KEYWORDS

switch, match, regular expression